Method of vinyl covering a refrigerator door panel

ABSTRACT

A vinyl plastic sheet is preformed by being positioned over a first rectangular vacuum forming female mold having undercut peripheral edges for forming a return flange border allowing the vinyl sheet to be heated and vacuum formed into a preformed cover with the aid of plug assists which are used to develop boxlike corners while preventing excess reduction in the sheet material thickness. The preformed vinyl cover is then loosely slipped over a refrigerator metal door panel on whose outer surface an epoxy adhesive solvent has been applied. The door panel and vinyl cover are next located in a second male mold and initially heated. Upon partial shrinkage of the cover a vacuum assist is established to cause the vinyl cover to conform to the door panel and return flanges whereby ridging of the material on the underside of the return flange corner junctures is prevented.

United States Patent Childress et al.

[ Nov. 6, 1973 METHOD OF VINYL COVERING A REFRIGERATOR DOOR PANEL Appl.No.: 216,096

Assignee:

U.S. Cl 156/245, 156/285, 156/287,

264/88, 264/90 Int. Cl. B29c 24/00 Field of Search [56/242, 245, 285,

References Cited UNITED STATES PATENTS 8/l934 Ritter l56/245 RADIANTHEAT 8/l972 Samuel et al. 156/245 X Primary ExaminerAlfred L. LeavittAssistant Examiner-Caleb Weston Att0rneyWilliam S. Pettigrew et al.

[57] ABSTRACT A vinyl plastic sheet is preformed by being positionedover a first rectangular vacuum forming female mold having undercutperipheral edges for forming a return flange border allowing the vinylsheet to be heated and vacuum formed into a preformed cover with the aidof plug assists which are used to develop boxlike corners whilepreventing excess reduction in the sheet material thickness. Thepreformed vinyl cover is then loosely slipped over a refrigerator metaldoor panel on whose outer surface an epoxy adhesive solvent has beenapplied. The door panel and vinyl cover are next located in a secondmale mold and initially heated. Upon partial shrinkage of the cover avacuum assist is established to cause the vinyl cover to conform to thedoor panel and return flanges whereby ridging of the material on theunderside of the return flange corner junctures is prevented.

1 Claim, 3 Drawing Figures METHOD OF VINYL COVERING A REFRIGERATOR DOORPANEL This invention relates to a refrigerator cabinet construction, andmore particularly with a method of forming refrigerator cabinet doorpanels covered with a decorative sheathing of vinyl plastic material.

Recently it has become popular to cover the door panels of refrigeratorcabinets with various decorative upholstering or plastic sheetingmaterial of various colors by means such as a removable trim striptypified by US. Pat. No. 2,760,301 issued Aug. 28, 1956 to Derr et al.Recent attempts to permanently bond plastic sheeting to appliance doorshave encountered the problem of providing a smooth, conforming coveringat the deeply drawn flange corner areas of the door panel without havingthe plastic sheeting on the underside bunch-up into raised bridges ormounds on the return portion of the flanged corners while obviatingextreme thinning of the drawn material to a point of possible rupture ortearing.

It is an object of this invention to provide a simple inexpensiveprocess for vacuum forming an integral vinyl sheet plastic decorativelaminate cover for a refrigerator rectangular door panel having returnflanges such that the plastic sheeting is bonded to and conforms withthe panel contours including the corner junctures formed by the panelreturn flanges.

Further objects and advantages of the present invention will be apparentfrom the. following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the Drawings:

FIG. I is a vertical section view illustrating the first step in vacuumforming the vinyl cover for use with the door panel; I

FIG. 2 is a vertical sectional view of the second step showing thecompletion of the vacuum forming process by means of a male mold;

FIG. 3 is a plan view of the female vacuum mold shown in FIG. 1.

Referring now to FIG. 1 there is shown a plastic vinyl sheet having atrim or scrap border 21 in position in a'female mold assembly generallyindicated at 22 in position to be preformed on the inner surface of themold 22. The sheet 20 is a polyvinyl chloride (P.V.C.) thermoplasticmaterial having a thickness within the range of approximately 0.035 to0.040 inches. The vacuum forming female mold assembly includes arectangular box-like fixture or vacuum pan 24 defining a chamber 25having an outwardly directed peripheral flange 26 on its side and endwalls. The chamber 25 of the pan 24 is adapted to be subjected to avacuum source (not shown) through a suitable pipe 30. An openrectangular frame or clamping ring 28 is clamped to the upper face offlange 26 by suitable clamp members (not shown). Positioned between theopposed ring and inwardly sloped perimeter 40 terminating in flushrelation with the outturned flange 26. In communication with therectangular box-shaped cavity 34 there are provided passages 35 throughwhich air. or gas may pass to evacuate the cavity. The textured vinylskin or sheeting 20 is located stretched in a horizontal plane over thefemale mold on the flange 26 as shown by its dashed line position 200 inFIG. 1. Heater means such as a Calrod resistance heater (not shown) islocated above the mold assembly 22 in a vertically adjustable mannersuch that it can be lowered to a predetermined height and energized todeliver radiant heat to the sheeting 20. In the preferred form theheater is lowered to a vertically disposed position approximately 20inches above the sheet 20 such that the vinyl sheet material is heatedwithin the range of 290 F. to 300 F. In the disclosed form thetemperature is recorded by the change in color of a series of thermotapestrips placed on the outer surface of the sheet by means of suitableadhesive tape. The thermotape strips are selected so as to provide anincremental series ranging from 270 F., 280 F., 290 F., 300 F., 310 F.and 320 F. In this way the operator is alerted to the fact that thesheet is approaching the desired temperature range.

The heater is then deenergized and a partial vacuum assist is applied bya suitable valve control (not shown) in pipe 30 until the vinyl sheetmaterial is located as shown in its solid line position 20b with sheetintermediate side walls 41 substantially perpendicular to the moldbottom wall 42 and its rectangular central portion 43 forced tightlyagainst the mold bottom wall, whereupon the vacuum assist is interruptedand held to m0- mentarily stop the flow of the vinyl sheet. Stateddifferently, the sheet material 20b is held just prior to its beingreverse formed by returning into the mold cavity undercut channel-shapedpocket region 44 defined by projection 38. Four plug assist members orhelper blocks indicated at 52 in FIGS. 1 and 3 in the form ofrectangular wooden blocks approximately 3 inches square and 1% inchesthick, are simultaneously placed in contact with the vertical innercomer surfaces of the sheeting 20b and moved diagonally outwardly in thedirection of the arrows such that the vinyl sheet material is forcedinto the four undercut female mold corners indicated by dash dot lineposition 200 to form box-shaped corners. After the plug assists 52 arelocated in the corner junctures the final vacuum assist is resumed tocause the remaining portionof the sheet side edge 54 and sheet returnhem 56 configured in an L-shaped trim to conform to the female moldsides 57 and undercut edges 58. The vacuum assist is retained until thevinyl sheet has cooled to room temperature.

The plug assists 52 further operate to chill the vinyl sheet material 20at the four corner junctures to thereby maintain the sheet materialthickness in the range of about 0.010 to 0.015 inch and thereby insureagainst the vinyl sheet being excessively thinned down in the comerregions. Such thinning is undesirable because of possible rupture of thesheet during the final panel covering operation or because of poor lifespan while in service'on the appliance door. 7

The vinyl sheet material is next cooled by suitable means such as blowerfans (not shown) located on the heater until the material has cooled andtaken a set whereupon the vacuum assist is removed and the preformedvinyl sheet is stripped from the mold.

A rectangular metal panel 62, including its: inwardly extendingperipheral flanges 64 and return flanges 66 has its outer surface 67coated with a heat sensitive adhesive containing randomly dispersedrelatively fine inert particles or glass beads of the type disclosed inU.S. Pat. No. 3,551,232 issued Dec. 29, 1971 to J. T. Thompson assignedto the same assignee as the present application, the disclosure of whichis incorporated by reference herein. The adhesive is currently availablefrom Inland Manufacturing Division of General Motors Corporation underthe name INLOCK Specification No. 56799-001. The adhesive is preferablyallowed a 24 hour drying period to insure that the panel surface is tackfree or not sticky. The untrimmed preformed sheet 20C is then slipped onthe door panel 62 for placement in the mold of FIG. 2.

As seen in FIG. 2 a second male mold assembly 60 includes the vacuum pan24 having suitable means such as support members 27 therein forreceiving a door panel support block 61 thereon. The block 61 has anupper horizontal surface 63 for supporting the vinyl covered door panel62. It will be noted that the trim or scrap border material 21 of thesheeting 20 is retaining so that it is again placed between the clampingring 28 and the flange 26 in a sealed manner as described for femalemold 22 prior to evacuation of the chamber 70 through the pipe 30. Theblock has passages 68, 69 through which air or other gas may pass so asto selectively evacuate the cavity 70. It will be noted that the block61 is conformed to limit the extent of coating on the return flange bymeans of vertical flange 72 such that in the preferred form the returnposition of the sheeting extends inwardly only approximately fiveeighthinch of the total flange extent of three-fourth inch. The male or blockmold 60 has a downwardly sloped border 74 complementary to the region40.

Reflectors 76 are configured to extend below the door panel returnflange 66 to supply reflected radiant heat to the underside edge 54 andhem 56 portions of the preformed sheet 20 of the flange. The overheadheater is again lowered to a position approximately 20 inches above thecovered door and radiant heat is applied to heat the sheeting 20 to asoftening temperature of abour 290 F. to 300 F. for about three minutes.Upon the preformed sheet conforming to the door panel and just prior tothe end of the 3 minute heating cycle a vacuum assist is applied tochamber 70 and by means of passage 68 to cavity 71 whereupon thepreformed vinyl sheet 20C returns or shrinks to the exact configurationof the door panel including the box corners defined by continuousperipheral flange 641 and return flange portion 66 of the cornerjunctures without causing the gathering of the sheet material and thedevelopment of excessive ridges or bulges thereat.

It has been determined that a shrink factor for the vinyl sheeting ofabout 0.010 of an inch per inch for both the width and length of thedoor panel will allow for the proper shrinkage of the preformed sheet onthe door panel.

We claim:

l. The method of vacuum forming a smooth flexible polyvinylchloridethermoplastic thin sheet cover having a thickness within the range ofapproximately 0.035 to 0.40 inches onto a rectangular metal door panelhaving an L-shaped continuous peripheral flange portion definingbox-shaped corner junctures comprising the steps of; providing a femalemold assembly including a rectangular vacuum pan having an outwardlydirected continuous clamping flange and a female mold insert positionedtherein, said female mold insert having a rectangular cavitycircumscribed by a continuous undercut channel-shaped peripheral pocketfor forming an L-shaped hemmed portion defining a rectangular areaaround the vinyl sheet of material from which the cover is to be formed,placing the vinyl sheet over said female mold assembly with itsdecorative outer side facing downwardly with the outer marginal trimedge of said vinyl sheet placed in sealed contact with the pan clampingflange, preheating the vinyl sheet to a temperature of about 290 to 300F. from a radiant heat source thereabove, removing the heat source andapplying a difference in pressure to opposite sides of the vinyl sheetin the form of a vacuum assist whereby the vinyl sheet centralrectangular area is forced intocontact with the bottom wall of saidcavity with the adjacent bordering portion of the sheet in vertical,flush relation with the open side of said channel-shaped pocket;interrupting the vacuum assist to momentarily stop the flow of the vinylsheet into the channel-shaped pocket, placing a rectangular plug assistat each corner juncture of the vinyl sheet and simultaneously movingeach of the plug assists diagonally outwardly into said female moldundercut pocket corners to force the vinyl sheet to conform with thefour mold undercut pocket corners, resuming the vacuum assist to causethe remaining portion of said vinyl sheet to conform to the remainingportions of the undercut channel-shaped peripheral pocket andmaintaining the vacuum assist until the sheet has cooled substantiallyto room temperature while said plug assists remain in said undercutpocket corners, applying a liquid adhesive layer including a pluralityof randomly distributed inert particulate fillers onto the outer surfaceof a rectangular metal panel including the continuous L-shaped flangeand allowing the adhesive to dry to a non-tacky state, removing thepreformed vinyl sheet from said female mold and enveloping therectangular sheet metal panel within the rectangular area of thepreformed vinyl sheet such that the decorative side of said vinyl sheetis exposed, providing a male mold assembly including said vacuum pan anda supporting buck portion inserted therein for receiving the innersurface of the metal panel, supporting the metal panel with the vinylsheet thereon over the buck portion of said male mold assembly such thatthe underside opposite said sheet decorative side of the marginal trimedge is placed in sealed contact with said pan clamping flange, placingradiant heat reflector means below the return flange portion of saidmetal panel continuous L-shaped flange, heating the vinyl sheet by meansof the radiant heat source for a predetermined period to a temperatureof about 290 to 300 F. whereby said reflector means directs radiant heatupwardly to the portion of the vinyl sheet covering the L-shaped flangeand applying a vacuum assist to cause said vinyl sheet cover to conformto said metal panel including its box-shaped corners so as to achieve ashrink fit by said vinyl cover without developing ridges on theunderside of the box-shaped return flange corners while limiting thedegree of thinning of said vinyl cover to the range of about 0.010 to0.0!5 inches at said corners.

* III III 1

